Re: [PATCH 2/2] virtio_balloon: export 'available' memory to balloon statistics

[Denis V. Lunev]

On 02/23/2016 06:10 PM, Michael S. Tsirkin wrote:
> On Tue, Feb 16, 2016 at 06:50:52PM +0300, Denis V. Lunev wrote:
> > From: Igor Redko <redkoi@xxxxxxxxxxxxx>
> >
> > Add a new field, VIRTIO_BALLOON_S_AVAIL, to virtio_balloon memory
> > statistics protocol, corresponding to 'Available' in /proc/meminfo.
> >
> > It indicates to the hypervisor how big the balloon can be inflated
> > without pushing the guest system to swap.
> >
> > Signed-off-by: Igor Redko <redkoi@xxxxxxxxxxxxx>
> > Reviewed-by: Roman Kagan <rkagan@xxxxxxxxxxxxx>
> > Signed-off-by: Denis V. Lunev <den@xxxxxxxxxx>
> > CC: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Oops - I missed the fact that this affects host/guest ABI.
>
> Can you please submit ABI update proposal to virtio tc?
> Spec patch would be even better.
>
> This is important to ensure there are no conflicts
> with other features being developed in parallel.

hmmm

From my point of view ABI remains untouched.
The guest can send any amount of <tag>;<value>
pairs and unknown tags are properly ignored
by the host.

That is why I think that this change is safe.